And I will place all my mountains. Here he directly and expressly treats of the return of the people; for in vain would he have promised so great happiness to the Church, if the people were not to be restored to their former liberty. The meaning is, that he will remove every obstacle and hinderance that might prevent the return of the people; and that he will render the "mountains" passable, which appeared to be impassable; and, in short, that he will level both the mountains and the valleys, that their return to Judea may be facilitated. Thus, when the Church is about to be completely restored, no obstructions, however great and formidable, can hinder God from being finally victorious. Besides, when he calls them "my mountains," he not only means that he has an absolute right to command them to afford a passage to his people, but declares that he will be the leader of the expedition, as if he would march along with the Jews, and accompany them in the joumey. In like manner, it is said in another passage, that he passed through Egypt and "rode on the high places of it" at the departure of his people. (Deuteronomy 32:13.) But here he describes the extraordinary love of God towards the Church, when he says that he travels along with her, and undertakes to supply all her wants, as if he were consulting his own interests when he assisted his people.

And I will make all my mountains a way - I will make all the mountains for a highway; or an even, level way. That is, he would remove all obstructions from their path. The image is taken from the return from Babylon to the land of Palestine, in which God so often promises to make the hills a plain, and the crooked places straight (see the notes at Isaiah 40:4).
And my highways shall be exalted - That is, the way shall be cast up (see Isaiah 57:14; Isaiah 62:10), as when a road is made over valleys and gulf (see the notes at Isaiah 40:4).

And I will make all my mountains a way,.... Or "for", or "into a way" (e); signifying that they should be dug through or levelled, and a way made through them, over them, or upon them, for his people to pass: very probably the allusion is to the mountains that lay between Babylon and Judea; and which the Lord calls his, because of his making and settling, and was therefore able to make them a way, or passable: though the words are not to be literally understood, but denote the removing of all impediments, obstructions, and difficulties, in the people's return from captivity; which was typical of redemption by Christ, which had its difficulties, which he only could get over; he came leaping over these hills and mountains, and they became a plain before him, the great Zerubbabel; such as the assumption of a sinless nature, to make atonement in for sin, which only could be produced in an uncommon and extraordinary way; the fulfilling of a broken law, satisfying divine justice, engaging with many enemies who were to be conquered, sin, Satan, the world, and death; bearing the wrath of God, and submitting to an accursed death: and so in the conversion of the Gentiles, which may here be referred to, and of any sinner, there are many mountains of difficulties in the way of it, which the Lord only can remove; great opposition is made by the men of the world to the preaching of the Gospel, the means of it to the work itself, by Satan, who is loathe to lose a subject of his kingdom; and by men themselves, whose carnal minds are enmity to God, and all that is good difficulties arise from the state of deadness, darkness, and hardness of heart men are in before conversion from the corruptions of their nature, and strong habits of sin; from the general depravity of all the powers and faculties of the soul; from the bad company they have got into; or from their own self-righteousness, they are loathe to part with: and when men are called, and a work of God is begun, there are many mountains appear in their way of coming to Christ; as their numerous and aggravated sins, and doubts about the willingness Christ to receive such sinners; but, when God works, nothing can let. Many are the obstructions the saints meet with in their passage, through this world, by reason of a body of sin, Satan's temptations, the world's persecutions, afflictions of various kinds, strait circumstances of life, losses, crosses, and disappointments; unbelief of itself is a mountain, and raises many others; but the Lord makes a way for his people through all; it may be some respect may be had to the spread of the Gospel in the world, and the introduction of latter day glory, and the difficulties in the way thereof, which the Lord has been removing, and will remove. Rome Pagan is one mountain which God has removed; and Rome Papal is another he will, move, with all the antichristian powers; and the Turkish empire is another:
and my highways shall be exalted; Christ is the great highway of all, and next his word and ordinances, which are ways of holiness and righteousness; these may be said to be "exalted", being conspicuous and visible; and, like causeways, or, highways cast up, that are above, and carry over the mire and dirt; so these carry over the mire and dirt of sin and corruption; and may be said to be so when made use of, approved, and valued: or the words may be rendered, "they shall be", or "let them be exalted on my highways" (f); that is, his people, being in the exercise of faith, and in the discharge of their duty; see Psalm 18:33 with these words compare Isaiah 40:3 perhaps this passage may be best explained by Revelation 16:12, where mention is made of the drying up of the river Euphrates, or of the destruction of the Ottoman empire, to make way for the conversion of the eastern nations, prophesied of, among others, in the following verse.
(e) "in viam", V. L. Piscator, Montanus, Cocceius; "ut siut pervii", Junius & Tremellius; "in viam planam", Vitringa. (f) "et in aggeribus meis emineant", Junius & Tremellius.

my--All things are God's.
mountains a way--I will remove all obstructions out of the way (Isaiah 40:4).
exalted--that is, cast up (Isaiah 57:14; Isaiah 62:10); for instance, over valleys. VITRINGA explains "mountains" as great kingdoms, Egypt, Syria, &c., subjected to Rome, to facilitate the spreading of the Gospel; "highways," the Christian doctrine wherein those who join the Church walk, and which, at the time of Constantine, was to be raised into prominence before all, and publicly protected (Isaiah 35:8-9).

A way - I will remove all hindrances, and prepare the way for them, by levelling high grounds, and raising low grounds.